Patent GB-851177-A (GB)
Title: Improvements in force measuring systems
Inventor: THORSSON MATTHEW THEODORE WESL
IPC: G01G3/147
Filed: 1956-12-28
Abstract: 851,177. Weighing systems. FAIRBANKS, MORSE & CO. Dec. 28, 1956, No. 39472/56. Class 40 (1). A weighing system in which the weight is displayed digitally comprises a device producing a voltage proportional to the weight and an automatically set balancing potentiometer comprising a number of sections connected in series and corresponding respectively to the digit positions of the possible weights and arranged so that the setting of each section alternately increases and decreases the balancing voltage, the sections being set in succession in response to the repeated passing of the balance point. The arrangement described is designed for four digits, each potentiometer section 13, 12, 11, 10, Fig. 2, being adjusted by a wiper switch having additional banks, Fig. 4, 34 for the thousands, 35, 48, 58 for the hundreds 36, 49 for the tens and 37, 50, 59 for the units, and further banks, Fig. 3, for controlling a lamp display. Preliminary operations. With sequence switch 30 ... 33, Fig. 4, in position 7 in which the value of the previous weighing is displayed, the operation of start key 97 releases relay 96 to complete a circuit for a pulse-generating valve 25 and to connect the sequence switch driving magnet 43 into circuit with interruptor contacts 115a driven by valve 25. In position 8, relay 84 moves its contact 84a to the right to deenergize the pulse generator and also energizes the homing banks 34 ... 37 of the potentiometer switches, which then home by selfinterruption, and the homing bank 33 of the sequence switch which also homes, the relapse of 84 being delayed in subsequent positions of the sequence switch and then by a capacitor to enable the homing operations to be completed. When 84 does fall back, the pulsing circuit is reenergized and the sequence switch is moved to position 1. Weighing operation. The output of a straingauge bridge 1, Fig. 2, associated with a load cell, corrected for the weight of the weighing platform &c. by a manually adjusted network 6 is opposed, in position 1 of the sequence switch, with all the potentiometers in their normal positions, by a voltage equivalent to 1010 pounds, the units and hundreds potentiometers normally registering their maximum values and the tens and thousands registering zero. If the cell voltage is the greater, contact 62 is operated and relay 64 prevents the further advance of the sequence switch. The pulsing circuit, however, remains energized and the thousands potentiometer is moved by its magnet 44 until the balancing voltage exceeds the cell voltage whereupon contact 62 is opened and contact 63 closed, and 64 falls back to prevent further stepping of the thousands potentiometer and to allow a further step of the sequence switch into position 2. The hundreds potentiometer is then stepped by its magnet 45 in a direction to reduce the balancing voltage, the sequence switch being stopped in position 2 by relay 64, energized on this occasion over contact 63. When the cell voltage again exceeds the balancing voltage, 63 opens releasing 64 to open the stepping circuit of the hundreds potentiometer and close that of the sequence switch. Similar operations take place in positions 3 and 4 of the sequence switch in which magnets 46, 47 drive the tens and units potentiometers. When the units potentiometer reaches the balance position, contact 63 opens and 62 closes. to step the sequence switch into position 5 in which 64 is energized independently of the contacts 62, 63. If either the hundreds or the units potentiometer reaches its extreme position, 64 is released at the off-normal bank 58 or 59. Carry-over arrangements. In position 5, if either the units or the hundreds potentiometer is in its normal position (representing 10 or 1000 1b.) stepping magnet 46, 44 of the potentiometer of the next higher denomination is energized to move the associated potentiometer one step. Moreover if the hundreds potentiometer is in position 9 and the tens potentiometer is in its maximum position, relay 57 is energized to cause an additional operation of the thousands potentiometer. After a delay sufficient to allow the carry-over arrangements to operate, relay 82 which was energized in position 4 falls back and allows the sequence switch to be stepped to position 6. Printing and display. In position 6, coil 83 is energized to initiate the operation of a printer (not shown) and open contacts 71 to prevent the advance of the sequence switch until the printer has completed its operation and closes contacts 73. In position 7, relay 96 operates to open the stepping circuit and connect the supply to the display lamps selected by the potentiometer settings. Potentiometers for the units, tens and thousands have been positioned with the help of the carry over circuits referred to above but the hundreds potentiometer remains in its originally set position and if the tens potentiometer is in its maximum (subtract) position, relay 57 is energized to connect up an alternative switch bank in which the lamp connections are displaced by one position with respect to the normal bank.